As an example, a braking device for a vehicle which applies braking force to the vehicle in response to the amount of braking operation by an operator of the vehicle is disclosed in a Japanese patent publication JP2008-87617 A (patent document 1). The braking device in the document is, for example, equipped with a master cylinder which supplies wheel cylinders with braking fluid. An electro-magnetic valve is provided in the hydraulic passage hydraulically connecting the master cylinder with the wheel cylinders. The electro-magnetic valve is of a type which controls flow of braking fluid in response to an electric power to be supplied thereto. A method for setting the operating characteristics of the electro-magnetic valve (such as a relationship between the valve opening current/valve opening electric power and the pressure difference) is disclosed in, for example, a patent publication JP2004-237982 A (patent document 2). According to this method, the operating characteristics of the electro-magnetic valve are determined by directly measuring the pressure at the upstream and downstream sides of the electro-magnetic valve.